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TUESDAY, June 17, 2003 (HealthDayNews) -- A girl's physical characteristics when she enters puberty may indicate how her health will fare as an adult, particularly when it comes to obesity and possibly breast cancer.
That's the conclusion of a controversial new study that some critics call a "giant leap of faith."
The 10-year project, which followed 859 girls beginning at age 10, found that those who developed breasts before body hair had a slightly higher percentage of body fat in the year before and the years following puberty. They also had an earlier onset of their first menstrual cycle.
Based on this finding, which appears in the June issue of the Journal of Pediatrics, study author Dr. Frank Biro speculates these girls may also have an increased risk of obesity and possibly breast cancer later in life.
"Previous studies have shown an association between breast cancer, an early onset of the menstrual cycle, greater body mass index and body fat," says Biro, a pediatrician at Cincinnati Children's Hospital Medical Center.
"Since the girls in our study who developed breasts as the first sign of puberty did get their first period early and did have more body fat, the speculation is that they might be at greater risk for breast cancer as adults," he adds.
Critics, however, counter that Biro's speculation is just that -- speculation -- and his yet-to-be-proven theories should not alarm young girls and their mothers.
"This theory involves a leap of many steps," says breast cancer expert Dr. Julia Smith, an oncologist at New York University. "Not only is there no proof that this is true, none of the variables have been controlled for. So we really must caution people reading the study not to assume that this information would affect the breast cancer risk profile of young women in any way."
Still, Biro insists his ideas are consistent with "the epidemiological profiles already in place for the development of certain health risks."
He notes that fat cells convert androgen hormones to estrogen, so the more fat cells a girl has, the more estrogen she will have. Biro believes this same excess estrogen is what encourages breasts to develop earlier than body hair in some girls. It's the extra estrogen and extra weight, along with the earlier onset of the menstrual cycle, that may translate into a greater risk of obesity and possibly breast cancer later in life, Biro speculates.
Smith doesn't see it that way.
"We don't even have proof that increased body weight or obesity is a direct link to the development of breast cancer in adulthood," Smith says. "So what that would mean in childhood is really very, very hard to speculate about."
The American Cancer Society says there's no evidence that weight gained in childhood increases the risk of breast cancer -- even if the weight gain persists into adulthood.
Moreover, Smith points out the girls in Biro's study who developed breasts first were not considered obese or overweight, and their rate of breast development could have been just weeks ahead of body hair. (Biro acknowledges the study did not document the length of time between breast development and the appearance of body hair.) And the difference in the start of first menstruation was, on average, less than seven months, Smith says.
"These measurements are hard to consider as statistically significant when looking at an end point like breast cancer, a disease that can have so many different variables and factors," says Smith.
The study initially involved almost 2,400 participants, although the final group consisted of 859 girls, all age 10 with no obvious signs of pubescent development.
The study followed the girls for approximately 10 years, during which time each received an annual pediatric exam that recorded their weight, height, body mass index (a ratio of weight to height) and indications of pubescent development.
Among the observations during the 10-year period: Girls who developed breasts before body hair had their first menstrual cycle, on average, seven months sooner than the other girls. They also had a small increase in their level of body fat and waist-to-hip ratio in the year prior to puberty. These differences remained during the course of the 10-year follow-up.
Based on these findings, Biro speculates the girls who developed breasts first may have a greater adult risk of obesity, and possibly breast cancer.
Smith does not agree.
"This is a leap that would involve a great deal of further investigation and again, I would caution anyone reading this study not to assume that this finding is in any way directly related to the development of breast cancer," says Smith.
More information
To learn more about puberty and adolescent health, visit KidsHealth.org. For information on breast cancer risks, check with the American Cancer Society.
